Obstructive sleep apnea (OSA) is a condition that affects an estimated 14 million Americans. The condition is caused by relaxation of soft tissue in the upper airway during sleep, resulting in its obstruction. OSA is characterized by a complete cessation of breathing during sleep for 10 or more seconds (apnea), or a reduction in breathing for 10 or more seconds causing a 4% or greater decrease in blood oxygen level (hypopnea). Individuals having 5 or more apneic or hypopneic events per hour are diagnosed as suffering from OSA. The obvious side effects of sleep apnea are daytime sleepiness and chronic fatigue. However, OSA is known to be a contributing factor in hypertension, heart disease, as well as other serious health conditions.
The most common treatment for obstructive sleep apnea (OSA) is positive pressure (above-ambient) applied at the patient's nose or mouth, or at both the nose and mouth. This treatment is also frequently prescribed to patients suffering from chronic obstructive pulmonary disease (COPD). FIG. 1 is a schematic diagram of an apparatus conventionally used in positive airway pressure (PAP) therapy treatment. The PAP device 120 supplies pressurized atmospheric air, which is conveyed through a hose 122 to a patient interface 124, adapted to deliver the pressurized air to the patient airway through either the nares 106, the mouth 108, or both the nares 106 and the mouth 108. The positive air pressure helps prevent obstruction of the patient airway. Treatment pressures typically range between 4 and 20 cm H2O for OSA, and up to 35 cm H2O for COPD, depending primarily on the severity of the condition.
Positive airway pressure devices 120 often also include other components or features that are adapted to increase patient comfort, or which may be used for diagnostic purposes. Examples include humidification of the treatment air to prevent dryness and soreness of the nose, mouth, and airway; filters designed to remove irritants and allergens from the treatment air; and, diagnostic recording instruments. It is, therefore, understood that a PAP device, in the current context, may also comprise any such additional features, wherein the primary medical function of the device is to supply pressurized air to the patient airway.
In order for positive airway pressure treatment to be effective, a mechanism for maintaining the patient interface 124 securely in position is required (not shown in FIG. 1). This requirement maintains a seal between the patient interface 124, and the nares 106 and/or mouth 108 of the patient, without which loss of applied pressure results, due to leaks in the system. Interface leaks can also cause arousal, either from the sensation of airflow on the face, or because of the sound generated by the increased airflow.
FIGS. 2a and 2b show, schematically, the principle of the most common type of support device for a respiratory interface. The apparatus consists of a frame 130, typically made of rigid plastic material, to which the interface 124 is attached, or into which it is integrated. One end of the interface 124 is formed to be suitable for delivering the treatment air to the nares 106 (FIG. 2a) or to the nares 106 and mouth 108 (FIG. 2b) of the patient. The other end of the interface 124 is adapted to receive pressurized air, supplied by the PAP device 120 through a length of hose or tubing 122. Elastic straps 132, or other similar mechanisms, are fixed around the head 102 of the patient, thus securing the frame 130 of the apparatus to the head 102 of the patient.
Ideally, in order to provide a proper seal between the interface and the patient, light pressure should be applied on the interface 124, in the direction toward the nares 106 and/or mouth 108 of the patient. With the apparatus shown in FIGS. 2a and 2b, the force opposing the sealing force is applied to the head 102 of the patient, through the frame 130 and/or straps 132 of the device. Since the nose and the skin of the scalp 102a are pliable, relatively minor movement or facial deformation of the patient may break the seal during sleep, or by the hose 122 tugging on the frame 130 or interface 124 of the apparatus.
To overcome the problem of sealing, various modifications and improvements to this type of interface support device have been devised (e.g. U.S. patent applications 2007/0017525 A1, 2006/0081252 A1, and 2006/118119 A1). These improvements typically involve means of more tightly securing the apparatus to the head 102 of the patient, by means of additional head-straps 132 or chin-straps 132a (FIG. 2c), as taught for example in U.S. patent application 2006/0283461 A1, and U.S. Pat. Nos. 6,470,886 B1, 7,047,971 B2, and 6,926,004 B2. The length, and therefore tension, of the straps 132 and 132a is also typically adjustable by the wearer by the use of hook-and-loop (Velcro™) fasteners, buckles, or any number of similar fasteners. While more rigidly fixing the support device to the head 102 of the patient, such measures result in additional pressure applied to the head 102 of the patient, which do not contribute directly to maintaining sealing pressure between the interface 124 and the patient. Prolonged use can result in mild headache or other discomfort, and may also leave marks or lines on head and face where the frame and/or straps contact the patient wearing the device. To alleviate this discomfort, the thickness of cushioning materials added to the areas contacting the patient is increased. However, the foam or gel materials typically used represent an additional layer of pliable material, which in turn requires greater tension on the straps, and increased pressure on the cranium.
In FIGS. 2a and 2b, the attachment 130a on the frame 130 of the device provided for the hose 122 is shown pointing substantially upward, and is located above the interface 124. However, in different embodiments of these prior-art inventions the hose 122 may approach the interface from the front, from below, or from one side of the interface 124.
Alternative measures for improving the sealing capability of interface support devices allow for manual adjustment of the position of the interface 124 relative to the frame 130. Examples, such as those taught in U.S. patent applications 2006/0213521 A1, 2006/0191539 A1, 2006/0032504 A1, and 2004/0060561 A1, include: plastically deformable elements such as pieces of wire, hinged joints, ball joints, and lead screws. Various means are used to maintain the position of these parts once adjusted, including mechanisms such as lock-tabs, snap-hooks, thumbscrews, or friction caused by close fit or slight interference between parts. Another invention uses flexible members as part of the frame 130 to provide some degree of automatic positional adjustment (e.g. U.S. Pat. No. 6,854,465 B2). Other inventions providing varying degrees of automatic positional adjustment, or a range of motion between the frame of the device and the interface, are provided in U.S. Pat. No. 7,096,867 B2, and U.S. patent applications 2006/0283456 A1 and 2006/0238459 A1. In yet another alternative (e.g. U.S. Pat. Nos. 6,347,631 B1 and 6,516,802 B2, and U.S. patent application 2002/0117177 A1), the frame is fitted to the occipital crown 102b of the patient, which eliminates, or at least reduces, the need for tensioning straps. However, in each of the above inventions, the primary solution is to restrain the motion of the frame by fixing it to a part of the head of the patient, thus placing strain on the head.
Still other devices (e.g. U.S. Pat. No. 7,066,179 B2, and U.S. patent application 2006/0283457 A1) comprise a hinged or rotatable fitting, such that the air hose 122 may approach the interface 124 from virtually any direction.
Other medical conditions exist for which treatment comprises delivery of a gas to the airway of a patient, and for which a patient interface support device is required. Most commonly, the gas is oxygen, or oxygen-enriched air delivered to a patient suffering from disease or injury causing loss of respiratory function. As shown in FIG. 3, a gas is supplied from a pressure-vessel and conveyed, through a pressure or flow-regulating valve, along a length of hose or tubing 144 to a suitable patient interface, such as the nasal cannula 146 shown in FIG. 3. The cannula 146 is typically fixed to the patient by securing the tubing 144 behind the head 102, or under the chin 104 of the patient, as depicted in FIG. 3. Adhesive tape 148 may also be additionally used to secure the tubing to the face or cheeks of the patient. As can be seen from FIG. 3, the hose or tubing cab easily become entangled with the patient. U.S. Pat. Nos. 5,279,486 A; 7,040,581 B2; 7,124,755 B2; and, U.S. patent application 2007/0045481 A1 disclose various devices which provide support for the supply hose and improve patient comfort. These types of construction have generally been devised to reduce leaks and discomfort caused by the supply hose becoming tangled or caught in the patient, or other objects such as patient bedding.
An alternative arrangement for securing the patient interface to the head of the patient consists of a dental appliance, which is molded around the teeth of the patient, and fixed to the upper mandible during use, as disclosed in U.S. Pat. No. 7,021,312 B2. The frame extends outside the mouth of the patient, and a means for rigidly attaching the nasal interface to the frame is provided. Optionally, the invention also provides a passage for air to enter the mouth of the patient. This apparatus provides a more rigid base for attaching the frame of the interface support device than the moveable and pliable skin of the cranium. However, wearing a device inside the mouth can also be a source of discomfort for some patients, even when properly fitted. Furthermore, while the invention eliminates strain placed on the cranium, the sealing force is now applied to the jaw of the patient, which may result in further pain and discomfort.
Although effectiveness of positive airway pressure treatment is well proven, approximately half of patients prescribed PAP for treatment of obstructive sleep apnea do not use their device regularly. Discomfort, including that caused by interface support devices, and arousal due to interface leaks, are both known to be contributing factors in this lack of treatment compliance. Therefore, there is a need for support devices designed to improve patient comfort by addressing these issues, which in turn will increase patient compliance.
It is, therefore, desirable to provide a support device that alleviates the strain on the patient's head by supporting the patient interface device while at the same time maintaining a seal between the interface device and the patient's airflow passages.